A surging Air New Zealand stands to benefit from lower fuel prices next year by up to $249 million but must now fend off growing competition from other airlines also enjoying lower oil prices.

Air NZ says a big surge in its capacity this year should lead to lower airfares.

Port of Tauranga said its net profit rose by 8.2 per cent to $42.6 million in the six months to December.

Ports of Auckland said its first-half net profit rose by 9.5 per cent to $28.9 million in the six months to December, driven by higher freight volumes.

Meridian Energy has raised its dividend and says it intends to return $625 million of capital to shareholders over the next five years.

New Zealand profit from the country's biggest general insurer, Insurance Australia Group, rose from $92 million to $193 million.

Trade Me Group, New Zealand's largest online auction site, posted slower profit growth in the first half of its financial year.

Meridian Energy, which generates about 30 per cent of the country's electricity, lifted first-half earnings 21 per cent.

Broker Forsyth Barr is tipping a drop in profit at Spark when the NZX's biggest listed company reports its half-year result tomorrow.

NZX chief executive Tim Bennett says demand is looking solid for small and medium-sized sharemarket listings, but a potential downturn in market conditions could affect the environment for initial public offerings in the year ahead.

Contact Energy shares have fallen nearly 9 per cent today after reporting a plunge in half-year profits.